Known examples of this type of working machine are provided by hydraulic working machines disclosed in Japanese Patent Laid-Open Publication No. 7-331707 and Japanese Patent Laid-Open Publication No. 11-100869. In the aforementioned hydraulic working machine according to Japanese Patent Laid-Open Publication No. 7-331707, if a breaker is operated in the state where a breaker mode is selected by a mode change switch, flow rate control is performed so that a hydraulic pump is brought in a constant low capacity state. Also, in the aforementioned hydraulic working machine according to Japanese Patent Laid-Open Publication No. 11-100869, if a breaker is operated by an operation pedal in the state where a breaker mode is selected by the mode change switch, the smallest discharging amount is selected from a discharging amount that is set by a maximum discharging amount setting section, a discharging amount that is subjected to positive control in accordance with the operation amount of the operation pedal, and a discharging amount that is subjected to P-Q control that limits the discharging amount so that the hydraulic pump may not be brought in an overload state. Thus, flow rate control is performed so that the discharging amount of the hydraulic pump is set to the selected discharging amount.